Recovery of soda in the manufacture of alumina.



UNITED STATES PATENT. OFFICE.

HARRY C. ZPEFFER, OF ST. LOUIS, ILLINOIS, ASSIG-NOR T0 ALUMINUM COMPANZOF AMERICA, 0F PIT'ISIBUBG, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA?RECOVERY OF SODA IN THE MANUFACTURE OF ALUMINA.

No Drawing- To all whom 'it may concern:

Be it known that I, HARRY C. PEFFER, a

citizen of the United States, residing at East St. Louis, St. Claircounty, Illinois, have invented a new and useful Improvement in theRecovery of Soda in the Manufacture of Alumina, of which the followingis a specification. 1

My invention relates particularly to a process'for the manufacture ofalumina in which bauxite is digested with carbonate of soda, lime, andsufficient water, as described in patent of Charles M. Hall, No.663,167,

' dated December 4th, 1900, and provides a novel and eflicient means forthe recovery of the soda which becomes combined with the red mud in thisprocess, and which has hith, erto been lost. In carrying out the processof the said patent, a certain amount of soda is rendered insoluble bycombination with silica, alumina or lime, in the solid residuum from thedigester process. I have discovered that by adding to thissnlid.residuum known as red. mud-a certain amount of caustic lime, andheating in a digester with water to about 350 C.;the soda is allrendered soluble and is removed. I

I have carried out the process in the ,fol-' lowing manner with goodresults, and give the figures for a laboratory operation, which canreadily be enlarged to an industrial scale. I take 400 grams 'of red mudby.

' dry-weight, 100 gramsof anhydrous caustic lime, and LOGO-cubiccentimeters of Water. The mixture is put into a closed digesterandheated at a pressure of 100 pounds to the square inch for one hour, Ashigh as 96 per cent. of the soda present in the mud may be in thismanner recovered in a soluble form, and is removed from the red merelyfiltering and washing.

Specification of Letters Patent.

mud. by

I do not limit myself to any particular- Patented Oct. 26, 1909.Application filed March 5, 1309. Serial No. 481,381.

may, to an extent at least, be obtained'by heating at a, lowertemperature and for a longer period, even without pressure. invention isalsonot limited to the method um left from thedigestion of bauxite withcaustic soda liquor, whether containing lime I alumina by the alkalineprocess from bauxof the patent above referred to, but may be,

used in the treatment of any red mud residuite, which consists in mixingthe red mud with lime and water and heating so as to render the sodaso'luble, and then filtering--- off the soda solution. 2. The method ofrecovering soda from the red mud residuum leftin the manufacture ofalumina from bauxite by .the alkaline process in which lime is used,which consists in adding additional caustic lime to the red mud anddigesting the mi'xture'with water under pressure, thereby renderingthe-soda soluble and then filtering and separating the soda. i a

v In testimony whereof, I have hereunto set; my hand.

, Hana-r c. Witnesses: i v i EDNA A. RAGLAND,

'I. M. QIEEAMBEBLIN,

